The present invention relates to a multiple image projection system for projecting two or more discrete images in adjoining relation on a view screen, and particularly relates to an optical system for projecting discrete multiple images in adjoining relation on a view screen to form a single seamless image thereon without substantial illuminance discontinuities at the juncture of the images. The present invention further relates to image projection displays of the liquid crystal display panel type, although the invention has applicability to other types of displays such as CRT projection systems. The invention is also not limited to either monochrome or color displays and embraces both rear projection and front projection installations.
In systems having a single light source illuminating a screen, the illumination on the screen at any point therealong is a function of the distance the screen lies from the light source and the inclination of the screen surface relative to the light source. In single image projection systems, the human eye is quite tolerant of illumination changes occurring over the surface of a screen and, thus, projector condenser lens systems having an acceptance cone angle of approximately 90.degree. are quite common. A discontinuity in illuminance, for example, when it is desired to project multiple images, however, is considerably less tolerable. An illuminance discontinuity of less than 5% is readily observable and undesirable. The cause of illuminance disparity when two or more images are projected and touch one another is a function, among other things, of the location of the observer. For example, if the observer is in front of a rear projection system using a pair of side-by-side projecting lenses to project two discrete images in side-by-side relation on a viewing screen, illuminance disparity does not occur if the observer views the screen from a point directly in front of the screen and equidistant from the projection lenses. When the observer, however, moves to one side or the other, the touching edges of the images become brighter or darker as a result of the different bend angles of the light rays emanating from the viewing screen from the different projection lenses.
There are other causes for this illuminance disparity which suggest other solutions, such as a low-gain screen. In general, however, such other solutions have not been effective to minimize or eliminate illuminance discontinuities at the juncture of multiple images in a projection system.
According to the present invention, the optical paths of the two or more images to be projected are combined to form a larger, single image displayed on a view screen by a novel and improved condenser and projection lens system without substantial illuminance discontinuity or a seam between the two projected images. Whereas previous systems for matching separate images at joining edges along a view screen employed separate projection lenses wherein the images were joined along opposite edges that did not pass through optical axes, the present invention provides for the juncture of the two images to pass through a single optical axis at the projection lens so that no mismatch or distortion occurs and illuminance discontinuity is substantially precluded.
In a preferred embodiment of the present invention, a pair of discrete images are disposed in adjoining relation on a view screen to form a single image thereon with minimal or no illuminance discontinuity at their juncture. To accomplish this, there is provided a light source, a condensing lens, a mirror system, a pair of discrete image displays, and a projection lens. The image displays may be LCD crystals or any other type of conventional image displays. An optical system including a lens and mirror is employed for transmitting the light rays from the light source separately through each of the image displays. That is, the lens and mirror project light rays from the source along discrete optical paths for passage separately through each image display. A single projection lens defining an optical axis is provided for projecting the images in adjoining relation on a view screen. Interposed between the image displays and the projection lens is an optical system including a lens and mirror for combining the light rays passing through the image displays along discrete optical paths for passage through the projection lens such that a single image combining the images from the discrete image displays in substantially seamless adjoining relation is formed on the view screen.
More particularly, the optical system between the image displays and the projection lens projects the light rays passing through each display for passage through the projection lens such that the light rays forming the adjoining edges of the discrete images on the view screen pass along the optical axis of the projection lens, whereby a single, substantially-seamless image is formed on the view screen.
A particular advantage of the present invention resides in the ability to physically join optically what cannot practically be physically joined in a mechanical sense. That is, because of construction methods, mounting circuitry, etc., liquid crystal panels, CRTs and the like cannot generally be physically joined to make a single, larger object. The present invention effects that image jointure optically.
More particularly, the optical system of the present invention is preferably comprised of an afocal pair of lenses. These lenses produce collimated light between them enabling their separation distances to be changed without affecting the optical characteristics of the system. Fresnel lenses could be used if desired. In the present system, the afocal lenses, in combination with mirrors or other lenses, allow part of the optical path to be diverted to one side, allowing separate transparent image displays, such as LCDs with interfering borders, to be optically combined in such manner that the borders do not appear in the image or interfere with the juncture of the images.
In a further embodiment of the present invention, additional image displays can be combined to form a single image on a viewing screen without illuminance discontinuities. For example, four image displays can be combined by using one quadrant of the illuminating light in the condenser lenses for each image display. In this case, four mirrors are required in each quadrant to form the optical paths through the lens system, and to divert the light rays from the image displays through the optical axis of the projection lens. Thus, four side-by-side images can be displayed as a single combined image on a viewing screen without substantial illuminance discontinuities.
In a preferred embodiment according to the present invention, there is provided an optical system for simultaneously projecting discrete images in adjoining relation on a view screen to form a single image therein with minimal illuminance discontinuities at their juncture, comprising a light source, at least a pair of discrete image displays, a lens system for projecting light rays from the source for passage separately through each image display, a projection lens for projecting an image on the view screen and defining an optical axis and means for projecting the light rays passing through each display for passage through the projection lens such that light rays forming the adjoining edges of the discrete images on the view screen pass along the optical axis of the projection lens, whereby a single image is formed on the view screen.
In a further preferred embodiment according to the present invention, there is provided an optical system for simultaneously projecting discrete images in adjoining relation on a view screen to form a single image thereon with minimal illuminance discontinuities at their juncture, comprising a light source, a pair of discrete image displays, a lens system for projecting light rays from the source along discrete optical paths for passage separately through each image display and a projecting lens for projecting an image on the view screen. Means are provided for combining the light rays passing through the image displays along the discrete optical paths for passage through the projection lens such that a single image combining the images from the discrete image displays in substantially seamless adjoining relation is formed on said view screen.
In a further preferred embodiment according to the present invention, there is provided an optical system for simultaneously projecting more than a pair of discrete images in adjoining relation on a view screen to form a single image thereon with minimal illuminance discontinuities at their juncture, comprising a light source, more than a pair of discrete image displays, a lens system for projecting light rays from the source along discrete optical paths for passage separately through each image display and a projecting lens for projecting an image on the view screen. Means are provided for combining the light rays passing through the image displays along the discrete optical paths for passage through the projection lens such that a single image combining the images from the discrete image displays in substantially seamless adjoining relation is formed on the view screen.
Accordingly, it is a primary object of the present invention to provide a novel and improved optical system for simultaneously projecting discrete images in adjoining relation on a view screen to form a single image substantially without illuminance discontinuities at their juncture.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.